Production of molded articles



UNITED YATES PATENT OFFICE.

THOMAS A. EDISON, OF LLEWELLYN PARK, WEST ORANGE, NEW JERSEY, ASSIGNOB,To NEW JERSEY PATENT COMPANY, OF WEST ORANGE, NEW JERSEY, A CORPORATIONor NEW JERSEY.

No Drawing.

1 0 all 2072071) it may concern:

Be it known that l, Tnoams A. Ems-on, a citizen of the United States,and a resident of Llewellyn Park, lVest Orange, Essex County, NewJersey, have invented certain new and useful Improvements in theProduction of Molded Articles, of which the following is a description.

My invention relates gene "ally to an improved method of producingmolded articles from material containing a substance comprisingingredients which react upon the application of sul'licieut heat to forma final hardened infusible condensation product, and more particularlyto a method of producing sound records in which the sound waves areimpressed in a surface layer or veneer formed of such a substanceapplied to a suitably shaped and preferably thermoplastic blank whichconstitutes a backing for the sound record.

The substance referred to may consist of any fusible resin of phenolicorigin mixed with any material containing the methylene radical CH whichis capable of reacting with the resin upon the application of heat toform a final hardened infusible condensation product; but in theproduction of a sound record comprising a backing or base having asurface layer applied thereto for receivlng the sound wave impressions,in connection with which I shall specifically describe my invention, Ipreferably employ as the substance from which the said surface layeris'formed a fusible phenol resin mixed with heXa-methylene-tetra-amineas the hardening agent, such as the lacquer or varnish described inUnited States Patent No. 1,098,608, grantedtJune 2,1914 to Jonas \V.Aylsworth. This substance also preferably contains a coloring pigment,such as lamp black, and a small amount of para-phenylene-di-amine toincrease the speed of the chemical reaction which causes the formationof the final hardened product upon the application of sufficient heat,as disclosed in United States Patent l :o. 1,283,706, granted to meNovember 5, 1918.

It has heretofore been customary in forming sound records such asdescribed above to provide the record blank or backing with the surfacelayer of varnish in its fusible state, that is, before the firsthardening or condensing reaction takes place, and to then impress thesound waves into such layer by Specification of Letters Patent.

Application filed April 30, 1919.

Patented Apr. 4, 1922.

Serial No. 293,595.

molding the coated blank or tablet under pressure and with theapplication of sufiicient heat to effect the final hardening reaction,whereby the surface layer of the record tablet as the latter is takenfrom the mold, will be in its final condensed infusible condition withthe sound waves permanently iormed therein. The hardening or condensingreaction requires a considerable time even when a relatively hightemperature is employed, and consequently, when this method is followed,the number of facsimiles which may be made from each matrix per day islimited, and it is necessary to employ a large number ol such matrices,which are very expensive, in order to obtain the required output of agiven sound record.

It has also been proposed to convert the surface layer or veneer of thecoated blank or tablet into the final hardened or com.- pletelycondensed state by heating or curing the coated blank to etlect andcomplete the final hardening reaction, before subjecting the same to themolding operation, and to thereafter form the sound record groove in thehardened surface layer by heating the latter sufficiently to render thesame Somewhat plastic andimpressing the sound record matrix thereinunder pressure. This [)TOCOSS, however, is objectionable, for during thefinal hardening reaction of the said veneer or coating, the solventtherein is driven oil and escapes from the outer surface of the veneerin the form of small bubbles, resulting in the formation of smallcavities throughout the veneer, that is, an increase in the porosity ofthe veneer, and therefore an interior surface for receiving the recordimpression.

The principal object of my invention resides in a method whereby morerecords of the character described herein may be obtained in a giventime from a single matrix than in the case where the curing orcondensing and hardening of the fusible condensation product of thesurface layer of the record blanks or tablets are wholly performedduring the molding of the sound records, and whereby the recordreceiving surfaces of the records obtained will be free fromimperfections which are produced, as described above, when the veneer orcoating of the record blanks is finally hardened prior to the moldingoperation; and my invention consists broadly in partially curing orcondensing the surface layer or veneer of the coated blank prior to themolding operation in order that the latter may be performed in lesstime.

In practicing my method in producing sound records of the characterabove described, I first coat the surface of a suitably shaped blank ortablet which is preferably quite porous, with a layer or veneer of thevarnish composed of the mixture of phenol resin and hexamethylene-tetra-aminein its fusible condition, and preferably in aliquid state, as by brushing. lVhen in a liquid state the varnishcontains a suitable solvent, preferably alcohol, in which the phenolresin is dissolved. The record blank or tablet to which the coating. isapplied preferably contains a suitable substance, preferably a resin,which renders the same the 'moplastic and which is also soluble in thesaid solvent. It will thus be apparent that some of the alcohol or othersolvent in the varnish penetrate the blank and dissolve a certain amountof the resin in the latter, and therefore that as the varnish dries, itwill be rigidly attached to the blank and substantially integraltherewith. After the application of the varnish, the coated blank isdried in the air for a short time until the surface layer becomessomewhat tacky or sticky. A great number of blanks coated and dried asjust described are then placed in an oven or other receptacle in whichthey are heated or baked for a considerable period, preferably about sixhours, during which the temperature of the oven is gradually raised fromroom temperature, that is, about degrees F., to a point preferablybetween 180 degrees F and 220 degrees F, and preferably about 200degrees F.

The heating or baking of the coated blanks in this manner cures thevarnish or surface layer thereof, bringing the same to a semicondensedor semi-final state, in which it is still somewhat soluble in alcohol.The blanks are now removed from the oven and allowed to cool. Thecondensation material. comprising the surface layer will then be in whatis known as the rubbery stage. \Vhen in this rubbery stage, the materialof the surface layer is neither hard nor sticky and may be readilyrendered sufficiently plastic, by the application of a small amount ofheat, to be easily impressed by the sound record matrix. Moreover. whenthe varnish is in this rubbery stage, the hardening or condensingreaction may be quickly completed to thereby obtain the final hardenedproduct, with the application of but a comparatively small additionalamount of heat. Each of such coated blanks. with its semi-cured. andsemi-condensed surface layer, is then placed in a printing mold. andsubjected to a con'maratively low pressure for a short period, duringwhich it is subjected to suflicient heat to render its semicondensed andsemi-cured veneer or surface layer thoroughly lastic. The holdingpressure is then gra ually increased until it is in the neighborhood of1000 pounds per square inch, and the record tablet is kept in the moldunder this pressure and preferably under a temperature substantiallyequal to that of steam at 125 pounds, for a period of about nineminutes, during which the sound waves on the matrix are, of course,impressed into the surface layer of the tablet and the final hardeningor condensing reaction of the material constituting the said surfacelayer is completed. During the final hardening of the surface layer inthis man ner, the alcohol or other solvent which may still be presenttherein will be driven therefrom back into the porous blank without anyresultant increase in the porosity of the sur face layer. The recordtablet is then suitably cooled while in the mold, and without reducingthe molding pressure, after which the pressure is released and thetablet removed from the mold.

lVhile I have described my improved method particularly in connectionwith the production of a specific form of sound record, it is to beunderstood that the same is adapted for making other forms of soundrecords and for many other purposes, and that the method is subject tovarious changes and modifications without departing from the spirit ofthe invention and the scope of the appended claims.

Having now described by invention, what 1 claim as new and desire'tosecure by Letters Patent is as follows:

1. The method of producing a molded article which consists in providinga member with a surface layer containing a fusible condensation product,curing said surface layer by the application of heat until the same isbrought to a semi-final or semi-condensed state, and then moldingsaidmember with the application of heat to further condense said surfacelayer, substantially as described.

2. The method of producing a molded article which consists in providinga member with a surface layer containing a fusible condensation product,curing said surface layer by the application of heat until the same isbrought to a semi-final or semi condensed state, and thenmoldingsaidmember with the application of sufficient heat to bring the materialof said surface layer to its final. hardened infusible state,substantially as described.

The vInetho'd'of producing a molded article, which consists insubjecting amember comprising a fusiblecondensation material to heatuntil such material is brought to a semi-final or semifcondensed state,and then molding said member with the application of snflicient heat tobring said material to its final hardened infusible state, substantiallyas described.

4. The method of producing a molded article, which consists in providinga member with a surface layer containing a fusible condensationmaterial, subjecting said memher to a gradually increasing heat untilthe surface layer is brought to a semi-final or semi-condensed state,and then molding the said member with the application of sufficient heatto complete the condensation reaction, substantially as described.

The method of producing a molded article, which consists in providing amember with a surface layer containing a fusible condensation material,subjecting said member for a period of substantially six hours to a heatgradually increased from room temperature to a point between 200 degreesF. and 300 degrees F. during such period, until the surface layer isbrought to a semifinal or semi-condensed state, and then molding thesaid member with the application of sufficient heat to complete thecondensation reaction, substantially as described.

6. The method of producing a molded article, which consists in providinga member with a surface layer containing a fusible condensationmaterial, curing said surface layer by the application of heat until thesame is brought to the rubbery stage, and then molding said member withthe application of sufficient heat to brin the material of said surfacelayer to a final hardened infusible condition, substantially asdescribed.

7. The method of producing a molded article, which consists in coating2. blank with a liquid varnish containing a fusible condensationmaterial, allowing the coated blank to dry in air, then heating saidblank until the coating thereof is brought to a semi-final orsemi-condensed state, and then molding the coated blank with theapplication of suflicient heat to bring the coating thereof to its finalhardened infusible state, substantially as described.

8. The method of producing a molded article, which consists in forming ablank containing a plasticity ingredient, coating said blank with aliquid varnish containing a fusible condensation product comprising aphenol resin and a solvent for the latter in which said ingredient issoluble, allowing the coating of said blank to dry in air, then heatingsaid coated blank until the coating thereof is brought to a semi-finalstate, and then molding the coated blank with the application ofsuflicient heat to bring the coating thereof to the final hardenedinfusible and insoluble state, substantially as described.

9. The method of producing a molded article, which consists in providinga member with a surface layer containing a fusible condensationmaterial, heating said member until said surface layer is brought to asemifinal state, then allowing said member to cool, then heating saidmember until the surface layer is plastic and molding said member withthe application of suflicient additional heat to bring said surfacelayer to its final hardened state, and then cooling said member withoutreleasing the molding pressure, substantially as described.

This specification signed this 24th day of April 1919.

THOS. A. EDISON.

